A heat pump controller for use in a heat exchange system includes a first input connector, a second input connector, and a computing device. The first input connector is configured to be coupled to a first sensor for receiving a first signal from the first sensor. The second input connector is configured to be selectively coupled to a second sensor for selectively receiving a second signal from the second sensor. The computing device is configured to initiate a defrost cycle, and is selectively configurable between a plurality of defrost modes including a first defrost mode and a second defrost mode. In the first defrost mode the computing device initiates the defrost cycle based on the first signal received from the first sensor and a period of time. In the second defrost mode, the computing device initiates the defrost cycle based on at least the second signal received from the second sensor.